A piezoelectric ceramic exhibiting a so-called piezoelectric phenomenon is known in which mechanical distortion and stress are generated when an electric field is applied. Such a piezoelectric ceramic is used in a vibrating element such as an actuator, a sound generator, a sensor, or the like.
Lead zirconate titanate (Pb(Zr,Ti)O3) with excellent piezoelectricity is most frequently used as the piezoelectric ceramic used in the above way. However, since lead zirconate titanate contains a large amount of lead, the influence on the global environment such as lead elution due to acid rain is regarded as a problem recently. Therefore, there is a need for lead-free piezoelectric ceramics to replace lead zirconate titanate, and various piezoelectric ceramics without lead have been proposed according to this requirement.
On the other hand, smaller size, higher performance and higher reliability are required with the electronic components, and the same trend is also found in piezoelectric components. Most piezoelectric components use a bulk body made by a sintering method, however, it occurs that processing for controlling the thickness becomes extremely difficult as its thickness becomes smaller and that the size of the crystal grain size causes deterioration of properties. As a means to solve this problem, researches on piezoelectric thin films made by various thin film forming methods and the application in the element using the same have been actively conducted in recent years.
For example, a sputtering method is a representative thin film forming method. Its mechanism is that a voltage is applied between a substrate (anode side) on which a thin film is to be deposited and a target (cathode side) made of material for thin film making which is opposite to the substrate in an inert gas atmosphere such as argon atmosphere, by which ionized rare gas atoms are forced to collide with the target which is a cathode material, and the constituent atoms of the target are knocked out by the energy, whereby a thin film is deposited on the opposite substrate.
In the film deposition using a sputtering method along with the miniaturization of electronic components, thin films with higher precision and higher quality are required. As to the requirement for thin films with higher quality, specifically, preparation of thin films with high density and less defect becomes a problem. In particular, defects generated in the thin film will cause defects such as generation of leakage current when the thin film is made into a product. Thus, various studies have been made, such as suppressing generation of particles or nodules.
For example, Patent Document 1 discloses a method of suppressing the generation of particles during the manufacturing of the thin film and suppressing the incidence of defective products of the dielectric film by devising a manufacturing method of a lead-based sputtering target.